Ink jet printers eject liquid inks through nozzles having a special structure in a jet form and deposit the inks on a recording medium such as a paper sheet with controlling their flying tracks to print characters, images, etc. and are widely used as the printers of facsimile machines, word processors, personal computers, etc. As a printing medium for ink jet-printing, an ink jet-printing medium is used, which has various properties required for ink jet-printing such as fixing and absorbing properties of the inks for ink jet-printing, density of prints, roundness of each dot shape, sharpness of the periphery of each dot, whiteness, water-resistance, size-stability against moisture absorbing and desorbing, and the like.
To improve the properties which relates to printing quality among these properties, it is effective to provide a coating layer containing a pigment which comprises silica as a main component, and most of commercially available paper sheets have such a coating layer. To increase the whiteness, fluorescent dyes, brighteners or color adjusters such as dyes, pigments, etc. are used.
The ink jet-printing media, in particular, those used to record photographs or graphic data are often used in applications where the media are exposed to light, for example, those hung on walls or those used as displays, or applications where the media are stored for a long time such as albums, work collections, etc. In those applications, the requirement for ink jet-printing media which have high printing quality and cause less discoloration or fading of prints is increasing. Furthermore, the requirement for the reduction of the cost is also increasing, since the currently available ink jet-printing media are expensive.
The pigment which is most widely used as the surface coating of the ink jet-printing media is silica. Silica has a very high surface activity and thus increases the printing quality, but it may accelerate the discoloration or fading of the dyes in the inks for ink jet-printing, or the fluorescent dyes and the brighteners or color adjusters such as dyes and pigments. In addition, silica is generally expensive and thus increases the cost of the ink jet-printing media.